Outside breaker, inside main breaker panel, so is it a sub?

Hi everyone! I was doing some work outside my house today, and this thought occurred to me. On the outside of my house, directly below the meter, is a 100amp breaker. There are no smaller breakers or circuits branching off of this box, it just goes directly from there to my 200amp indoor breaker box (which I believe is acceptable even though the outside switch is only 100amp). I've never opened up that outdoor breaker to see how it is wired, but it appears to only have space for that one 100amp breaker, and there isn't any space for any other breakers to ever be added.

My question is, since I have that first breaker on the outside, is that actually my main, and my inside breaker box is then a sub panel? There are currently only 3 wires (two insulated, one bare 4 awg copper all jacketed together as SE-U) coming from that outdoor breaker into my indoor breaker box. I was just thinking that maybe that outdoor breaker could be making my indoor breaker box a sub panel, in which case it would really need 4 wires and a split ground and neutral, right?

Hopefully I'm just being paranoid, and the outdoor breaker isn't automatically making my indoor box a sub. I'm looking to sell my house and I want everything to be up to snuff beforehand.

I really appreciate your thoughts! I'm a rare poster, but a frequent reader!

1) I apologize if I'm not using the correct terminology, is the "grounding electrode" the copper ground rod? If so, I'm not sure exactly where it is connected, either to the meter socket or that outside box (again, I haven't opened it). It definitely isn't wired to the panel in the house.

2) If I read the jacket of the wire correctly, all 3 are 4awg. I find that to be rather small, but it looked like that might be ok based on a google search of table 310.15(B)(6)?? Please correct me if I'm misunderstanding that!

I should note that I didn't do any of this wiring, it was like that when I bought the place several years ago. I live in a rural community that had absolutely no licensing or inspections until a few years ago, so who knows if anything was ever right!

And yes, this outdoor breaker shuts off the indoor power, that is its sole purpose. So - if that makes the indoor panel a sub panel, how do I fix the issue?

1) I apologize if I'm not using the correct terminology, is the "grounding electrode" the copper ground rod? If so, I'm not sure exactly where it is connected, either to the meter socket or that outside box (again, I haven't opened it). It definitely isn't wired to the panel in the house.

2) If I read the jacket of the wire correctly, all 3 are 4awg. I find that to be rather small, but it looked like that might be ok based on a google search of table 310.15(B)(6)?? Please correct me if I'm misunderstanding that!

I should note that I didn't do any of this wiring, it was like that when I bought the place several years ago. I live in a rural community that had absolutely no licensing or inspections until a few years ago, so who knows if anything was ever right!

And yes, this outdoor breaker shuts off the indoor power, that is its sole purpose. So - if that makes the indoor panel a sub panel, how do I fix the issue?

Well, I'm having trouble sleeping so I just got out of bed and saw your posts. After this one, I'm trying to go back to sleep so don't expect any replies till tomorrow

Plummen: Nothing really made me worry I guess, I just have done a lot of studying of the electrical forums for a garage subpanel project I've been planning at another property, and I got all the info about separating the ground and neutrals on sub panels. Then today out of the blue, I just happened to think about my house electric and how that indoor panel maybe needs another wire. And sorry, I don't have any pictures, I've never even opened up that outdoor box (I'm a little nervous around power I can't shut off). The indoor panel can be safely shutoff outside, but the outside panel can't be shut off without having someone pull the meter. You wanted to know, it is copper 4awg, it says THHN or THWN SE Style U.

Julius: I'm just trying to learn, I'm not questioning your experience, but why does table 310.15(B)(6) indicate that the 4awg copper is acceptable? What I found was 2008 NEC. Am I not understanding correctly when that table should be used?

Apparently I've got a couple of issues at play here - typical! Thanks for the responses so far!

Well, I'm having trouble sleeping so I just got out of bed and saw your posts. After this one, I'm trying to go back to sleep so don't expect any replies till tomorrow

Plummen: Nothing really made me worry I guess, I just have done a lot of studying of the electrical forums for a garage subpanel project I've been planning at another property, and I got all the info about separating the ground and neutrals on sub panels. Then today out of the blue, I just happened to think about my house electric and how that indoor panel maybe needs another wire. And sorry, I don't have any pictures, I've never even opened up that outdoor box (I'm a little nervous around power I can't shut off). The indoor panel can be safely shutoff outside, but the outside panel can't be shut off without having someone pull the meter. You wanted to know, it is copper 4awg, it says THHN or THWN SE Style U.

Julius: I'm just trying to learn, I'm not questioning your experience, but why does table 310.15(B)(6) indicate that the 4awg copper is acceptable? What I found was 2008 NEC. Am I not understanding correctly when that table should be used?

Apparently I've got a couple of issues at play here - typical! Thanks for the responses so far!

Thank you,saved me a lot of looking for my book

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Julius: I'm just trying to learn, I'm not questioning your experience, but why does table 310.15(B)(6) indicate that the 4awg copper is acceptable? What I found was 2008 NEC. Am I not understanding correctly when that table should be used?

Apparently I've got a couple of issues at play here - typical! Thanks for the responses so far!

Very good question and the answer is like this. Even though thhn is rated for 90 degrees it can't be used for it in most situation. The reason for that is being that the lugs, circuit breakers Ect.. Are only rated for 75 degrees. Therefore you will be limited to the 75 degree column. Now when using romex you will be limited to the 60 degree column.

Are some of you saying that because I have a meter main, that makes my breaker panel a subpanel? I've never heard that before. My house is only three years old, and I'm pretty sure there aren't four wires feeding the breaker panel. When did that become a requirement? My county was using NEC 2005 when the house was built.